Pitx2: Molecular Mechanisms in Eye Development and Disease

描述：调节眼前节结构正常发育的遗传网络知之甚少。小鼠是确定正常眼睛发育的基本机制和分析遗传性眼病的理想模型。同源异型盒基因PITX 2的突变导致Axenovir-Rieger综合征（ARS），一种常染色体显性疾病，引起先天性眼前节缺陷和青光眼。我从小鼠中克隆了Pitx 2，并在小鼠中使用基因靶向技术来产生一系列Pitx 2等位基因，这些等位基因允许基因功能的全局或条件性消融，以及改变基因剂量的能力。基于已发表的数据和我们自己的初步结果，我们假设Pitx 2在眼周间充质中的核心作用，在眼发育过程中，用于分化来自间充质的眼细胞类型，以及用于眼表面和神经外胚层正常发育所需的外源因子的间充质表达。在上一个资助周期中，我们证明了Pitx 2在眼神经嵴和中胚层中的早期表达，确定了Pitx 2在神经嵴中的功能是眼睛发育中多个步骤所必需的，并确定了PITX 2在调节神经嵴中Wnt信号传导中的作用，这可以解释Pitx 2突变表型。该提案的总体目标是使用我们的一系列小鼠Pitx 2等位基因来确定Pitx 2在眼睛发育过程中在中胚层中的作用，并建立Pitx 2与Wnt信号通路组分之间的机制和功能关系。在目标1中，我们将使用条件性靶向策略来检验Pitx 2在眼部中胚层中具有不同功能的假设。在目标2中，我们将测试特定的Wnt信号通路基因作为PITX 2的直接靶点，并确定其在眼睛发育中的形态学和分子作用，以确定该基因是否占Pitx 2表型的组成部分。我们还将筛选具有特定眼前节缺陷和青光眼的人类患者的该基因突变。在目标3中，我们将直接测试小鼠中Pitx 2和Wnt途径基因之间的遗传相互作用，作为Pitx 2突变表型修饰的机制，因为表型变异性是ARS的关键特征。这种多方面的方法将提供有关Pitx 2在眼睛发育中的功能的具体机制细节，以及在此过程中更普遍的眼周间充质基本机制的新知识。这些基本信息对于了解包括青光眼在内的眼科疾病至关重要。

DESCRIPTION: Genetic networks regulating normal development of anterior segment structures are poorly understood. Mice are ideal models for determining the basic mechanisms contributing to normal eye development and for analyzing genetic eye disease. Mutations in the homeobox gene PITX2 result in Axenfeld-Rieger Syndrome (ARS), an autosomal dominant disease causing congenital anterior segment defects and glaucoma. I cloned Pitx2 from mouse and used gene targeting in mice to generate a series of Pitx2 alleles that allow for global or conditional ablation of gene function, and the ability to vary gene dose. Based on published data and our own preliminary results, we hypothesize a central role for Pitx2 in periocular mesenchyme during eye development for differentiation of ocular cell types derived from mesenchyme and for mesenchyme expression of extrinsic factors required for normal development of surface and neural ectoderm in the eye. In the previous grant cycle, we demonstrated early Pitx2 expression in ocular neural crest and mesoderm, established that Pitx2 function in neural crest is required for multiple steps in eye development, and identified a role for PITX2 in regulating Wnt signaling in neural crest that could account for Pitx2 mutant phenotypes. The overall goals of this proposal are to use our series of murine Pitx2 alleles to determine the role(s) of Pitx2 in mesoderm during eye development and to establish the mechanistic and functional relationships between Pitx2 and components of the Wnt signaling pathway. In Aim 1, we will test the hypothesis that Pitx2 has distinct functions in ocular mesoderm using a conditional targeting strategy. In Aim 2, we will test a specific Wnt signaling pathway gene as a direct PITX2 target and identify its morphological and molecular roles in eye development to see if this gene accounts for components of the Pitx2 phenotype. We will also screen human patients with specific anterior segment defects and glaucoma for mutations in this gene. In Aim 3, we will directly test for genetic interactions between Pitx2 and the Wnt pathway gene in mice as a mechanism for modification of the Pitx2 mutant phenotype since phenotypic variability is a key feature of ARS. This multifaceted approach will provide specific mechanistic details about the functions of Pitx2 in eye development and new knowledge into more general fundamental mechanisms of periocular mesenchyme in this process. This basic information is essential for understanding eye disease, including glaucoma.